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Solar Installation on Flat Roof in High Wind Area

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  • Solar Installation on Flat Roof in High Wind Area

    I have an installation question before I dig too deep into something I can't do:


    I live in a house in SoCal in a hilly area with a flat roof (slight angle, but basically flat), it gets REALLY windy once a year at least. In 2011 a windstorm came through that blew so hard that it peeled the roof covering back, and then it rained and screwed the whole house up for over a year, very stressful. I'm told that that's a once in 100 year storm, but who knows for sure? It was up over 80mph for sure, maybe higher. Trees were knocked over, power was out for days, lots of damage, it was bad. Now I have a new roof, and lots of other stuff.

    So my house was nailed, most of my neighbors were spared getting much less severe damage. One of whom got Solar Panels shortly before or after that storm, but it's so hilly around here that his situation is not the same as mine when it comes to the hills amplifying the wind.

    So what I'm wondering is: What do people in Hurricane prone or frequent wind storm areas do who are in a similar situation to myself? I'd assume for good functionality the panels would need to be at an angle since I have a flat roof, then again that would make them more susceptible to being blown off, would it not? Anyone have any experience with this?

    There's a couple of variables where hills may interfere with the solar panels getting enough light and all that, but before I get into that I need to know if I can safely mount solar panels without making my roof more easily damaged or risk of the panels blowing off, stuff like that.

    Thanks!

  • #2
    I don't know, but http://www.renewableenergyworld.com/...-the-wind.html has some great pictures of solar panels destroyed by wind

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    • #3
      Most all building codes require improvements to be designed such that the result has a sane probability of withstanding reasonably severe wind loadings
      (and other loadings as appropriate). Procedures exist to estimate such loadings and engineering designs are supposed to be done in such a way as to account for and accommodate such loadings. Building depts. are charged with checking to ensure such procedures are done by persons/organizations appropriately knowledgeable in those things.

      That happens most of the time.

      If you have unusual conditions, or have a concern about the situation, make those things known to the people designing the system, and don't allow anything to happen that you feel is less than adequate. Be prepared for some sticker shock if the engineering gets involved. You want nice - you pay nice. And, you get what you pay for - or less, depending on diligence.

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      • #4
        Originally posted by J.P.M. View Post
        Most all building codes require improvements to be designed such that the result has a sane probability of withstanding reasonably severe wind loadings
        (and other loadings as appropriate). Procedures exist to estimate such loadings and engineering designs are supposed to be done in such a way as to account for and accommodate such loadings. Building depts. are charged with checking to ensure such procedures are done by persons/organizations appropriately knowledgeable in those things.

        That happens most of the time.

        If you have unusual conditions, or have a concern about the situation, make those things known to the people designing the system, and don't allow anything to happen that you feel is less than adequate. Be prepared for some sticker shock if the engineering gets involved. You want nice - you pay nice. And, you get what you pay for - or less, depending on diligence.
        My concern is that if there are a lot more DIY installs that end up getting blown off the roof and damaging a neighbors property you will start to see some push back by the insurance companies which may require not only sturdier framework but drawing signed of by a structural Engineer. If the pv installer fails to get that documentation the insurance company may deny and compensation for damages. That will drive the cost of an install up.
        Last edited by SunEagle; 04-17-2016, 06:34 PM. Reason: spelling

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        • #5
          Originally posted by SunEagle View Post

          My concern is that if there are a lot more DIY installs that end up getting blown off the roof and damaging a neighbors property you will start to see some push back by the insurance companies which may require not only sturdier framework but drawing signed of by a structural Engineer. If the pv installer fails to get that documentation the insurance company may deny and compensation for damages. That will drive the cost of an install up.
          Mine too, which is one reason of many why I'd not consider owning a home previously owned by a DIYer.

          DIY or not, by the rules of the road in most areas with building codes, part of the design will be considerations for wind/seismic and other types of loadings. Now, I'm not so naïve as to think every PV system on every roof was put up there with a stamped and sealed set of calcs and drawings. However, that does not remove the responsibility on the part of the owner to ensure such things are done and done correctly and conscientiously. If there is push back from any source, it ought to be first from neighbors whose safety and housing values will be among the first affected.

          There are common standards that can be followed. Many racking outfits have cookie cutter calcs that can often be massaged into a design and run past building depts. That however, says little or nothing about what the array/racking will be attached to and how the rest of the structure will react to the added loads - for example, uplift caused by wind loading on an angled array anchored to a flat roof on a very old building.

          There are a lot of ways to cheap out on a design. Some are just dumb ideas. Skipping some of the engineering is not only cost ineffective in the ling run, particularly when discovered, but it also affects safety.

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          • #6
            I have seen wind damage or destroy a few of my trees here. But so far, panels thoroughly anchored in the ground
            haven't been affected. Bruce Roe

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            • #7
              Originally posted by bcroe View Post
              I have seen wind damage or destroy a few of my trees here. But so far, panels thoroughly anchored in the ground
              haven't been affected. Bruce Roe
              Wind speed is lower close to the ground than at treetop height, fortunately.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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              • #8
                Originally posted by inetdog View Post

                Wind speed is lower close to the ground than at treetop height, fortunately.
                I agree unless the ground is a slope close to the top of a mountain.

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